Vehicle cooling systems are becoming more complicated with the need to cool components, such as water cooled charge air coolers, automatic transmission coolers and hybrid vehicle coolers, at temperatures below which a normal engine cooling system runs. As a result of the need for colder coolant temperatures, these components are very often cooled by a separate cooling circuit. Such a separate cooling circuit is typically provided with coolant from an electric water pump and a dedicated heat exchanger.
In addition, the separate cooling circuit may comprise a separate expansion reservoir, which may provide a volume for the coolant to expand and deaerate into. The expansion reservoir may also provide a location to fill the coolant in the separate cooling circuit. However, separate coolant reservoirs may require additional fill equipment which may increase the cost and complexity of such cooling systems. Further, it is inconvenient for a vehicle user to have to monitor and fill up separate expansion reservoirs.
Accordingly, some previously-proposed dual temperature cooling systems have a single expansion reservoir. Both a higher temperature cooling circuit (for engine cooling) and a low temperature cooling circuit (for the water cooled charge air coolers, batteries, etc.) are linked by a connecting hose to allow filling of both circuits. However, the inventors herein have recognized potential issues with such systems, mainly due to the transfer of heat from one circuit to another. For example, the coolant in the low temperature circuit may be warmed resulting in higher temperatures than desired and thereby impairing the performance of dependant systems. Similarly, the coolant in the main engine cooling circuit may be cooled by the interaction with the low temperature circuit. This interaction may degrade heater performance and engine fuel economy.
In one example, the issues described above may be at least partially addressed by an engine cooling system comprising: an expansion reservoir, a first cooling circuit and a second cooling circuit, the second cooling circuit configured to operate at a different, e.g., lower, temperature than the first cooling circuit, wherein the expansion reservoir is configured to receive coolant from and return coolant to the first and second cooling circuits, wherein the expansion reservoir comprises one or more valves arranged so as to control, e.g., selectively restrict, the flow of coolant from the second cooling circuit to the expansion reservoir and/or from the expansion reservoir to the second cooling circuit depending on the temperature of the coolant.
As another example, the first and second cooling circuits may be in fluidic communication with each other via the expansion reservoir. However, the one or more valves of the expansion reservoir may substantially prevent flow between the expansion reservoir and one of the first and second cooling circuits when the coolant temperature exceeds a threshold value. As a result, the fluidic communication and thus thermal communication between the first and second cooling circuits may be restricted. As such, warming of the coolant in the cooler, second cooling circuit may be reduced. Thus, the cost, size, and complexity of the cooling system may be increased, while the efficiency may be increased.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.